ABSTRACT For decades, the nation?s rapidly aging population and rising need for family caregivers have been called to attention. Indeed, with earlier hospital discharges, the demands placed on caregivers continue to intensify. This is perhaps most pronounced in caregivers of patients undergoing allogeneic hematopoietic cell transplantation. Over the last three decades, caregiver interventions have been shown to be effective in improving caregiver well-being. However, most of them have focused on the negative aspects of caregiving (e.g., burden) with very few focused on the positive aspects of caregiving (e.g., benefit). Further, outcomes have traditionally relied on long-term recall and snapshot self-report. Thus, there has been limited understanding of the mechanism of action of an intervention. Mobile health technology has been shown to deliver flexible and time- and cost-sparing interventions to support caregivers across the care trajectory and enable the collection of continuous, multi- parameter physiological data. These highly time-resolved parameters correlated with snapshot self-report data have potential to provide new mechanistic insights of an intervention. The objective of this proposal is to leverage technology to deliver a novel caregiver-facing mobile health intervention guided by a conceptual framework of Carbonneau?s positive aspects of caregiving. Our interdisciplinary team will take our recent success of developing a multi-component, caregiver-facing mobile health product (BMT Roadmap) and further expand and test the intervention (Roadmap 2.0) in a randomized controlled trial. Our central hypothesis is that a multi- component technology-mediated intervention with focus on the positive aspects of caregiving will improve caregiver well-being. The study will be conducted in two phases. During Phase 1, we will identify positive constructs that reflect that caregiving process among diverse stakeholders, expand the system with new components, and pilot test Roadmap 2.0 through an iterative user-centered design process. Phase 2 will involve a two-arm study design where participants will be randomized to a treatment arm (mobile platform + Roadmap 2.0) or to a control arm (mobile platform + usual care) following a baseline assessment. The duration of the study will involve an active ~18-week intervention phase. We will recruit and randomize ~166 caregivers and patients (332 total). Participants will be assessed at baseline, day 30, and day 120 post-transplant. The primary outcome measure will be caregiver PROMIS Global Health at day 120. Secondary measures will include indices assessing positive aspects of well-being (e.g., self-efficacy, positive affect) and negative aspects of well-being (e.g., depression, anxiety, sleep disturbance). We will conduct a rigorous mixed methods process evaluation to determine the active and less active components of the system on caregiver and patient outcomes. We will also employ a novel data-driven approach to further identify optimal intervention components, dosage, and time that can be examined in future work. Our long-term goal is to implement and disseminate a scalable product that enhances caregiver health and well-being, while being seamlessly integrated into their daily lives.